Motor control devices hitherto available include a type that is configured to adjust a transfer characteristic of a predistorter to make it equal to a transfer characteristic from a state-quantity command value to a state-quantity detected value for a controlled object having a dead time. Such a motor control device thus reduces a deviation between a state quantity and a state quantity command, and obtains a high following performance.
A motor control device disclosed in patent literature 1 is one example of such motor control devices.
FIG. 4 is a block diagram showing a conventional motor control device. As shown in FIG. 4, controlled object 206 of this example is a motor and a load attached to the motor. As for controlled object 206, a position defined as a state quantity changes with a torque defined as a manipulation quantity.
Position detector 207 detects a position of controlled object 206, and outputs a position detected value. Feedforward controller 201 generates a feedforward manipulation quantity based on a position command value provided by a host controller. Predistorter 202 generates a position command corrected value based on the position command value.
Feedback controller 203 generates a feedback manipulation quantity based on a difference between the position command corrected value and the position detected value. Torque controller 205 makes use of the sum of the feedforward manipulation quantity and the feedback manipulation quantity as a torque command value. Torque controller 205 controls the torque so that the torque becomes equal to the torque command value. Adjustment calculator 209 adjusts predistorter 202 according to the position command corrected value and the position detected value.
Predistorter 202 is implemented by means of an infinite impulse response (“IIR”) adaptive filter of a digital controller in order to set a transfer function of predistorter 202 as close to a feedforward error as possible. The feedforward error is a difference between a transfer function of controlled object 206 and a transfer function of a controlled object model used for feedforward controller 201. Adjustment calculator 209 calculates and sets a filter factor of predistorter 202 from the position command corrected value and the position detected value according to an adaptive law.